Method of preparing a bodied siloxane resin including M, Q, and T-propyl units and capped with additional M units

ABSTRACT

A bodied siloxane resin comprises M, Q, and T-propyl units and is capped with additional M units. The bodied siloxane resin contains less silanol groups than the bodied siloxane resin before being capped with additional M units.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 13/179,148, filed on Jul. 8, 2011 which is acontinuation-in-part of U.S. Non-Provisional patent application Ser. No.10/585,837 filed on Jul. 12, 2006, which is a U.S. national stage filingof PCT International Patent Application Serial No. PCT/US2005/002451filed on Jan. 20, 2005, which claims the benefit of U.S. ProvisionalPatent Application Ser. No. 60/541,002 filed on Feb. 2, 2004, thedisclosures of which are hereby incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

Siloxane resins are important in many applications, such as protectivecoating applications.

One particular subclass of siloxane resins, bodied siloxane resins, hasfound particular utility in protective coating applications. However,bodied siloxane resins may be unstable, and their properties may degradeover time. For example, the molecular weight of the bodied siloxaneresins may increase after aging. This aging may also lead to an increasein the viscosity of the bodied siloxane resin, or the viscosity of asolution containing the bodied siloxane resin. This increase inviscosity is particularly undesirable in protective coatingapplications.

While the use of bodied siloxane resins in protective coatingapplications has led to desirable properties, a need exists to alter theproperties of the bodied siloxane resins used in such compositions.

SUMMARY OF THE INVENTION AND ADVANTAGES

A bodied siloxane resin comprising M, Q, and T-propyl units and cappedwith additional M units is provided. The bodied siloxane resin cappedwith additional M units contains less silanol groups than the bodiedsiloxane resin before being capped with additional M units.

The bodied siloxane resin capped with additional M units has an improvedstability over the bodied siloxane resin before being capped withadditional M units. The bodied siloxane resin capped with additional Munits has a molecular weight that does not increase significantly, afteraging, from the initial molecular weight.

DETAILED DESCRIPTION OF THE INVENTION

A bodied siloxane resin comprises M, Q, and T-propyl units and is cappedwith additional M units. Typically, the bodied siloxane resin cappedwith additional M units contains less silanol groups than the bodiedsiloxane resin before being capped with additional M units. The bodiedsiloxane resin capped with additional M units according to thisinvention has utility in a wide variety of applications including, butnot limited to, protective coating applications.

“The bodied siloxane resin capped with additional M units” ishereinafter referred to as “the post-capped bodied siloxane resin.”Further, “the bodied siloxane resin before being capped with additionalM units” is hereinafter referred to as “the bodied siloxane resin.”

M, D, T, and Q units and nomenclature relying on such units are known inthe art. For instance, an MTQ siloxane resin includes M units, T units,and Q units.

The term “bodied” refers to a siloxane resin that has undergone aprocess of bodying. Bodying is a process designed to increase themolecular weight of conventional siloxane resins to make them moredesirable in applications that use such conventional siloxane resins.During the bodying process, it is believed that a portion of excesssilanol groups are reacted from the conventional siloxane resin to bebodied such that some of the low molecular weight material of thesiloxane resin interacts to form a conventional high-molecular weightbodied siloxane resin. Bodying may be completed by heating the siloxaneresin to be bodied in the presence of suitable catalysts, such asalkaline or acidic catalysts. Other methods of bodying are alsocontemplated.

References to the bodied siloxane resin are intended to mean acombination of, or a reaction between an unbodied T-propyl siloxaneresin and an unbodied MQ siloxane. The bodying of the unbodied T-propylsiloxane resin with the unbodied MQ siloxane resin results in the bodiedsiloxane resin having a higher molecular weight than the unbodiedT-propyl siloxane resin or the unbodied MQ siloxane resin.

As used herein, the term “capped” refers to the reaction of silanolgroups present in the bodied siloxane resin with a silicon-containing Mgroup capping agent, which is described in greater detail below.

The post-capped bodied siloxane resin contains less silanol groups thanthe bodied siloxane resin. The additional M units are bonded in place ofsome of the silanol groups. It is theorized that the reduction in thenumber of silanol groups leads to improved stability. The M units maybond at a variety of locations on the bodied siloxane resin, dependingon the location of the silanol groups. This improved stability isevident during aging, during accelerated aging, and during solventexchange operations. The improved stability may also be evident when thepost-capped bodied siloxane resin is utilized in downstream formulationsin combination with other materials.

In one configuration, the bodied siloxane resin comprises from 0.02 to0.50 moles of silanol groups per mole of silicon with the caveat thatthe bodied siloxane resin contains more silanol groups than thepost-capped bodied siloxane resin. Alternatively, the bodied siloxaneresin comprises from 0.05 to 0.30 moles of silanol groups per mole ofsilicon, or from 0.05 to 0.15 moles of silanol groups per mole ofsilicon.

In one embodiment, the post-capped bodied siloxane resin typicallycomprises from 0.02 to 0.20 moles of silanol groups per mole of silicon.In an alternative embodiment, the post-capped bodied siloxane resincomprises from 0.03 to 0.15 moles of silanol groups per mole of silicon,or from 0.05 to 0.10 moles of silanol groups per mole of silicon.

When the bodied siloxane resin is capped with the M units, the amount ofsilanol groups decreases from >0 to <0.10 moles of silanol groups permole of silicon from the bodied siloxane resin to the post-capped bodiedsiloxane resin. Alternatively, the amount of silanol groups decreasesfrom >0 to <0.05 or from >0 to <0.03 moles of silanol groups per mole ofsilicon from the bodied siloxane resin to the post-capped bodiedsiloxane resin.

The molecular weight of the bodied siloxane resin or the post-cappedbodied siloxane resin may increase during the aging process. Themolecular weight instability can cause conventional bodied siloxaneresins to possess undesirable characteristics. The natural aging processcan be simulated by heating a sample in an oven over an extended periodof time. This simulated aging allows the prediction of the molecularweight instability as would typically be experienced by conventionalsiloxane resins during the natural aging process.

Simulated aging is conducted with an oven that is maintained at atemperature of about 110° C. Simulated aging may be conducted withheating equipment other than ovens and other temperatures may be used tosimulate aging. The initial molecular weight (M_(wi)) refers to themolecular weight of the bodied siloxane resin or the molecular weight ofthe post-capped bodied siloxane resin, respectively, before they undergosimulated aging. The aged molecular weight (M_(wa)), refers to themolecular weight of the bodied siloxane resin or the molecular weight ofthe post-capped bodied siloxane resin, respectively, after they havebeen aged at 110° C. for 70 hours.

The post-capped bodied siloxane resin undergoes less of a molecularweight increase during the aging process than the bodied siloxane resin.In one embodiment, M_(wa) increases 100% or less from the M_(wi) of thepost-capped bodied siloxane resin. In another embodiment, M_(wa) of thepost-capped bodied siloxane resin increases 50%, 25%, 15%, 5%, or 3% orless from the M_(wi) of the post-capped bodied siloxane resin.

The post-capped bodied siloxane resin may include the units: (R¹₃SiO_(1/2))_(a); (R² ₂SiO_(2/2))_(b); (R³SiO_(3/2))_(c); and(SiO_(4/2))_(d). ‘a’ (the mole fraction of M units) may range from 0.05to 0.5, or from 0.15 to 0.30, or from 0.15 to 0.20. ‘b’ (the molefraction of D units) may range from 0 to 0.3, from 0 to 0.2, or from 0to 0.1. ‘c’ (the mole fraction of T units) is typically >0, 0.30, 0.40,0.50, 0.60, 0.70, 0.80, 0.90, or 0.95. ‘d’ (the mole fraction of Qunits) may range from 0.05 to 0.60, from 0.15 to 0.45, or from 0.20 to0.30. In the above formula, a+b+c+d=1.

In embodiments in which the post-capped bodied siloxane resin includesthe units set forth above, the bodied siloxane resin before being cappedwith additional M units typically comprises the units: (R¹₃SiO_(1/2))_(a′); (R² ₂SiO_(2/2))_(b′); (R³SiO_(3/2))_(c′); and(SiO_(4/2))_(d′). Generally, the value of a′ is within the rangeprovided above for a, the value of b′ is within the range provided abovefor b, the value of c′ is within the range provided above for c, and thevalue of d′ is within the range provided above for d. In this formula,a′+b′+c′+d′=1. Additionally, this formula is subject to the proviso thata is greater than a′.

The post-capped bodied siloxane resin comprises M, Q, and T-propylunits. As will be understood by one of ordinary skill in the art, thepost-capped bodied siloxane resin may generally be describedcompositionally in the same manner as the bodied siloxane resin withregards to the D, T, and Q units. However, the post-capped bodiedsiloxane resin includes more M units than the bodied siloxane resin.

The R¹, R², and R³ in the post-capped bodied siloxane resin is eachindependently selected from a substituted or unsubstitutedcarbon-containing group comprising from 1 to 10 carbon atoms, an aminogroup, and a sulfido group. The substituted or unsubstitutedcarbon-containing group comprising from 1 to 10 carbon atoms may be morespecifically selected from substituted or unsubstituted hydrocarbylgroups containing from 1 to 10 carbon atoms. For the purposes of thedescription of this invention, a substituted hydrocarbyl group does notexclusively contain hydrogen and carbon atoms, i.e., the substitutedhydrocarbyl group contains at least one atom, other than hydrogen andcarbon atoms. Exemplary hydrocarbyl groups include, but are not limitedto, alkyl groups (substituted and/or unsubstituted), alkenyl groups(substituted and/or unsubstituted), aryl groups (substituted and/orunsubstituted), and carbinol groups. More specific examples include, butare not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, andoctyl; phenyl, naphthyl, benzyl, tolyl, xylyl, xenyl, methylphenyl,2-phenylethyl, 2-phenyl-2-methylethyl, chlorophenyl, bromophenyl andfluorophenyl, with the aryl group typically being phenyl.

In one or more embodiments, at least 0.40 moles of R³ group per mole ofsilicon are propyl groups. Alternatively, at least 0.50, 0.60, 0.70,0.80, 0.90, 0.95, 0.99, or 1.0 moles of R³ group per mole of silicon arepropyl groups. In another embodiment, 1.0 mole of R³ groups per mole ofsilicon are propyl groups.

The method of producing the post-capped bodied siloxane resin includescapping the bodied siloxane resin with a silicon-containing M groupcapping agent to form the post-capped bodied siloxane resin. Thesilicon-containing M group capping agent comprises at least 0.5 moles ofmonofunctional units per mole of silicon. The post-capped bodiedsiloxane resin comprises the reaction product of the bodied siloxaneresin, which comprises M, Q, and T-propyl units, and thesilicon-containing M group capping agent.

The silicon-containing M group capping agent may comprise at least oneR¹ ₃SiO_(1/2) unit, at least one disiloxane, or at least one disilazane.In one embodiment, the silicon-containing M group capping agentcomprises a compound having the following average formula:

In this formula, ‘Z’ is Cl, an alkoxy group containing from 1 to 10carbons, or a hydrocarbyl group containing from 1 to 10 carbon atoms;each R⁴, R⁵, and R⁶ is independently a hydrocarbyl group containing from1 to 10 carbon atoms; ‘X’ is O or NH, and ‘y’ ranges from 0 to 10. Inone specific embodiment, ‘y’ ranges from 0 to 1. Although certainsilicon containing M group capping agents are enumerated throughout thisdisclosure, other conventional capping agents are also contemplated foruse. Alternatively, hydrolyzates of the compounds set forth above may beutilized as the silicon-containing M group capping agent.

The silicon-containing M group capping agent may also be a chlorosilane,an alkoxysilane, a disiloxane, or a disilazane. The silicon-containing Mgroup capping agent may comprise a monofunctional silane, a siloxane, ora silazane. Suitable monofunctional silanes include, for example,triorganosilanes, such as halo-, alkoxy-, and carboxy-triorganosilanes.More particularly, specific examples of the silicon-containing M groupcapping agent include trimethylchlorosilane, trimethylmethoxysilane,hexamethyldisiloxane, diphenylmethylmethoxysilane,dimethylphenylmethoxysilane, diphenylmethylchorosilane,dimethylphenylchlorosilane, hexamethyldisilazane, and hydrolyzatesthereof. In one embodiment, the silicon-containing M group capping agentcomprises trimethylchlorosilane. Mixtures of silicon-containing M groupcapping agents may also be used if desired.

The amount of silicon-containing M group capping agent may range from0.01 to 0.5 parts by weight of silicon-containing M group capping agentper part by weight of the bodied siloxane resin. Alternatively, theamount of silicon-containing M group capping agent may range from 0.05to 0.3, or 0.10 to 0.20 parts by weight of silicon-containing M groupcapping agent per part by weight of the bodied siloxane resin.

As referred to herein, by “contents,” it is intended to mean a compoundor mixture of compounds present in the reaction vessel after addition ofthe silicon-containing M group capping agent, the bodied siloxane resinand various other components. Furthermore, it will be appreciated thatthe composition of the contents changes as the method proceeds throughthe various steps, through reactions, phase changes, distillation ofcertain components, and addition of new components.

A variety of reaction vessel types may be used with the method describedherein. In one or more embodiment, the reaction vessel may be mixedusing an agitator, stirring paddle, or other mixing technique.Alternatively, the contents of the reaction vessel are mixed andagitated with a series of mixing loops and mixing chambers. The reactionvessel may also be equipped with an inert gas purge. The inert gas purgemay comprise nitrogen, argon, or other inert gas type that isnon-reactive with the contents of the reaction vessel.

The step of capping the bodied siloxane resin may comprise a firstheating step. The first heating step may include heating the contents ofthe reaction vessel to a temperature ranging from 25 to 60° C., or from35 to 55° C. The first heating step may have a duration ranging from 30to 600 minutes, or from 60 to 180 minutes.

After first heating step is completed, the contents of the reactionvessel may include the post-capped bodied siloxane resin, residualsilicon-containing M group capping agent, reaction byproducts, and anorganic solvent. Depending on the silicon-containing M-group cappingagent utilized, the contents may include acidic or basic species.Typically, the contents may be processed in order to provide aneutralized product having an acid or base content ranging from 0 to500, or 0 to 100 ppm of the acidic or basic species. The method mayfurther comprise removing the residual silicon-containing M groupcapping agent and the reaction byproducts from the contents to form theneutralized product or a product having greater purity.

The step of removing the residual silicon-containing M group cappingagent and the reaction byproducts may include performing a series ofdistillations. Water may be added before each subsequent distillation inorder to aid with the removal of the reaction byproducts. In oneembodiment, the step of removing the residual silicon-containing M groupcapping agent includes a preliminary distillation step, a primarydistillation step, and a secondary distillation step.

The preliminary distillation step may include distilling the residualsilicon-containing M group capping agent from the contents of thereaction vessel at a temperature ranging from 100 to 150° C. at ambientpressure in the absence of water.

The primary distillation step may include adding water to the contentsof the reaction vessel and subsequently heating the contents of thereaction vessel to a temperature ranging from 100 to 150° C. at ambientpressure to remove the water, residual silicon-containing M groupcapping agent, and reaction byproducts through distillation.

The secondary distillation step may include adding water to the contentsof the reaction vessel and subsequently heating the reaction vessel to atemperature ranging from 100 to 150° C. at ambient pressure to removewater, residual silicon-containing M group capping agent, and reactionbyproducts through distillation.

The pressure of the preliminary, primary and second distillation stepsmay each independently range from 20 to 100 mmHg. As will be appreciatedby one of ordinary skill in the art, as the pressure rises, greatertemperatures will also be required.

The step of removing water, residual silicon-containing M group cappingagent, and reaction by-products from the contents of the reaction vesselmay be conducted in any number of steps sufficient to form theneutralized product or the product having greater purity. Furthermore,other techniques of removing the water, residual silicon-containing Mgroup capping agent, and reaction by-products are contemplated, such asthrough the addition of a neutralizing agent and subsequent filtration.

As mentioned above, the bodied siloxane resin may be provided in theorganic solvent. In one embodiment, the organic solvent comprises one ormore hydrocarbons, such as aromatic hydrocarbons. In one specificembodiment, the organic solvent comprises toluene and xylene.Alternatively, the organic solvent may comprise benzene, toluene,xylene, or similar aromatic hydrocarbons; hexane, heptane, isooctane, orsimilar linear or partially branched saturated hydrocarbons; andcyclohexane, or similar aliphatic hydrocarbons; and blends thereof maybe suitable. Excess organic solvent may be added to the mixture alongwith a co-solvent, such as an organic alcohol. Alcohols suitable forthese purposes include, but are not limited to, methanol, ethanol,n-propyl alcohol, isopropyl alcohol, butanol, methoxy ethanol, ethoxyethanol, or similar alcohols.

If the bodied siloxane resin is capped with the silicon containing Mgroup capping agent in the presence of the organic solvent, then themethod may further comprise conducting a solvent-exchange between theorganic solvent and the alternative carrier solvent.

The alternative carrier solvent may comprise isododecane,2-butyloctanol, isohexadecane, C₁₂₋₁₅ alkyl benzoate, castor oil,hydrogenated palm oil, glycerin, or isopropyl palmitate. Alternatively,the alternative carrier solvent may comprise a cyclic siloxane, shortchain siloxane, or some other form of hydrocarbon solvent. Short chainsiloxane fluids are typically understood to mean those siloxanes fluidshaving a molecular weight (M_(w)) ranging from 200 to 700. If thealternative carrier solvent used in the solvent-exchange step is ahydrocarbon solvent, an aliphatic hydrocarbon solvent is preferable.

During the solvent exchange step, the post-capped bodied siloxane resinand the organic solvent are heated during a first distillation stepunder reduced pressure to remove a portion of the organic solvent viadistillation. The temperature of the first distillation step may rangefrom 50 to 150° C. The pressure of the first distillation step may rangefrom 20 to 100 mmHg. As will be appreciated by one of ordinary skill inthe art, as the pressure of the first distillation step rises, greatertemperatures will also be required.

The solvent exchange step may also include the addition of thealternative carrier solvent to the post-capped bodied siloxane resin inthe reaction vessel. The addition of the alternative carrier solvent maybe conducted after the first distillation step.

The solvent exchange step may further include a second distillationstep. During the second distillation step, the reaction vessel andcontents thereof may be heated to a temperature ranging from 50 to 150°C. and a pressure ranging from 20 to 100 mmHg. In addition, before thesecond distillation step, additional alternative carrier solvent may beadded.

The solvent exchange step may include additional distillation stepsother than the first distillation step and second distillation stepdescribed immediately above. Furthermore, the addition of alternativecarrier solvent may be repeated intermittently before or after thecompletion of any distillation steps until the post-capped bodiedsiloxane resin contained in the alternative carrier solvent has anon-volatile content ranging from 10 to 90%, or from 40 to 75%.Alternatively, other techniques of solvent exchange may be utilized withthe method and compositions disclosed herein.

The bodied siloxane resin may be exemplified by, but not limited to, thefollowing formulas:((CH₃)₃SiO_(1/2))_(a)(CH₃CH₂CH₂SiO_(3/2))_(c)(SiO_(4/2))_(d);((CH₃)₃SiO_(1/2))_(a)((CH₃)₂SiO_(2/2))_(b)(CH₃CH₂CH₂SiO_(3/2))_(c)(SiO_(4/2))_(d);((CH₃)₃SiO_(1/2))_(a)((CH₃)₂SiO_(2/2))_(b)((CH₃)(C₆H₅)SiO_(2/2))_(b′)(CH₃CH₂CH₂SiO_(3/2))_(c)(SiO_(4/2))_(d);(CH₃)₃SiO_(1/2))_(a)((CH₃)₂SiO_(2/2))_(b)(CH₃CH₂CH₂SiO_(3/2))_(c)(C₆H₅SiO_(3/2))_(c)(SiO_(4/2))_(d);((CH₃)₃SiO_(1/2))_(a)((CH₃)₂SiO_(2/2))_(b)((CH₃)(C₆H₅)SiO_(2/2))_(b′)(CH₃CH₂CH₂SiO_(3/2))_(c)(C₆H₅SiO_(3/2))_(c)(SiO_(4/2))_(d).In the above formulas defining the siloxane resin, ‘a’ ranges from 0.05to 0.5, the sum of ‘b’+‘b′’ ranges from 0 to 0.3, ‘c’ ranges from 0.05to 0.65, and ‘d’ ranges from 0.05 to 0.6.

A polyorganosiloxane can optionally be included in the method herein.Polyorganosiloxanes which may be added include D units and/or T units.The polyorganosiloxane can be added to introduce various D and/or Tunits into the bodied siloxane resins (before or after capping withadditional M units) to alter its properties. The structure or formula ofthe polyorganosiloxane is not restrictive, providing thepolyorganosiloxane contains some measurable quantity of D units or Tunits.

The polyorganosiloxane may contain any combination of M, D, T and Qunits, provided at least some D or T units are present. Thus, thepolyorganosiloxane can be selected from any of the fluid, gum, orresinous silicones known in the art comprising D or T units, orcombinations thereof. The D units typically contain methyl or phenylsubstituent groups, which can be designated as D^(Me) and D^(Ph)respectively, or any combinations thereof. The T units typically containmethyl or phenyl substituent groups, which can be designated as T^(Me)and T^(Ph) respectively, or any combinations thereof. Thepolyorganosiloxane can be a linear polydiorganosiloxane fluid having aviscosity of 10-1000 mm²/s. Typically the polydiorganosiloxane fluid ispolydimethylsiloxane, or a polymethylphenylsiloxane. Thepolyorganosiloxane can also be an organosilsesquioxane. Theorganosilsesquioxane resin typically is a methylsilsesquioxane resin ora phenylsilsequioxane resin.

Furthermore, any individual D, T or Q units of the bodied siloxaneresins can also contain a hydroxyl group and/or alkoxy group.

The post-capped bodied siloxane resin described herein may be producedwith a batch, semi-continuous, or continuous process.

The following examples are intended to illustrate the invention and arenot to be viewed in any way as limiting to the scope of the invention.Furthermore, as used below, GPC³ refers to triple detection gelpermeation chromatography. The GPC³ test was performed with a ViscotekT-305 Triple Detector Array along with a Viscotek GPC Max.

In order to perform the GPC³ test, samples to be analyzed were firstdiluted in Tetrahydrofuran (THF) (0.100 g sample dissolved in 5 g THF),filtered with a 0.45 micrometer polytetrafluoroethylene filter. Theinjection volume for the GPC³ analysis was 200 microliters. Columns usedfor the GPC³ analysis includes: three PL gel Mixed B's and a guardcolumn. Columns and all detectors were heated to 35° C. The GPC³instrument was calibrated with a 100 μL injection of ASTM certifiedpolystyrene, having a molecular weight (M_(w)) of 113,500.

EXAMPLES

Preparation of the bodied siloxane resin comprising M, Q, and T-propylunits: an MQ resin solution (171.21 g of 70.3% non-volatile content inxylene), a solution of propylsilsesquioxane (346.27 g of 80.9% NVC intoluene), xylenes (283.20 g), and KOH solution (4.5 g of 48% KOH indeionized water) were added to a reaction flask. The reaction mixturewas heated with removal of water via azeotropic distillation, followedby two hours heating at 136° C. After cooling below 40° C., glacialacetic acid (0.39 g) was added to neutralize the basic catalyst. Afterfurther cooling to 25° C., the reaction mixture was further dried byadding anhydrous magnesium sulfate (20 g), and then stirred for onehour. The product was pressure-filtered (0.45 micron filter paper),yielding ˜700 g of a slightly hazy, colorless liquid. Non-volatilecontent testing (2 grams product solution in 2-inch aluminum pan heatedto 150° C. for 2 hours) indicated the solution contained 49.5 wt % NVC.GPC³ indicated a resin weight-averaged (M_(w)) molecular weight of323,000 Daltons. ²⁹SiNMR (20 wt % product NVC in CDCl_(3′)0.02 MCr(acac)₃) indicates silanol content is 0.016 g OH per gram resin NVC.

Capping of the bodied siloxane resin with a silicon-containing M groupcapping agent: the bodied siloxane resin (250.20 g solution, at 49.53%NVC) and 4.00 g of chlorotrimethylsilane (4.00 g) were combined in aflask. The reaction was heated to reflux (54-55° C.) for two hours, andthen cooled to ambient temperature. The reaction flask was fitted with aDean-Stark apparatus itself fitted with a water-cooled condenser, andthe reaction mixture heated to 138° C. and approximately 20 g ofcondensate collected and removed, then the reaction mixture cooled to55° C. The Dean-Stark trap was then refilled with fresh xylene anddeionized water (approx. 2 g) added to the reaction mixture. Thismixture was heated to distill and remove residual chlorotrimethylsilane,chloride ions, and water over approximately 90 minutes. After cooling toambient temperature, xylene (16.49 g) was added, yielding 202.49 g of aclear, light yellow product solution. Non-volatile content testing (2grams product solution in 2-inch aluminum pan heated to 150° C. for 2hours) indicated the solution contained 50.0 wt % non-volatile content.GPC³ indicated a resin weight-averaged (M_(w)) molecular weight of377,000 Daltons. ²⁹Si NMR (20 wt % product NVC in CDCl_(3′)0.02 MCr(acac)₃) indicates silanol content is 0.010 g OH per gram resin NVC.

Stability Study of Post-capped Bodied Siloxane Resins: Simulated agingwas begun by adding approximately three grams of a sample to an aluminumpan, which was placed in a 110° C. oven. Five samples of each resin wereprepared. At defined heating times, samples were removed from the oven,cooled, and their analysis compared to that of the initial solutions.Testing of each aged sample involved adding xylene to the aged sampleand determining whether it could be re-dissolved or had gelled. If thematerial could be re-dissolved, a sample of aged material was alsodissolved in 2 wt. % concentration in THF and submitted for tripledetector GPC³ analysis. The stability of the bodied siloxane resin wasevaluated. Furthermore, the stability of the post-capped bodied siloxaneresin was evaluated.

TABLE 1 Aging of the Bodied Siloxane Resin Heat Aging Time (h) Solublein Xylenes GPC³ M_(w) 0 Y 323,000 2 Y 1,320,000 4 N Gelled 10 N Gelled29.5 N Gelled 78 N Gelled

TABLE 2 Aging of the Post-Capped Bodied Siloxane Resin Heat Aging Time(h) Soluble in Xylenes GPC³ M_(w) 0 Y 377,000 2 Y 398,000 4 Y 379,000 10Y 376,000 29.5 Y 388,000 78 Y 415,000

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. It is intended that the invention not belimited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method of preparing a post-capped bodiedsiloxane resin, said method comprising: capping a bodied siloxane resincomprising M, Q, and T-propyl units with a silicon-containing M groupcapping agent in a reaction vessel to form the post-capped bodiedsiloxane resin.
 2. The method of claim 1 wherein the step of capping thebodied siloxane resin with the silicon-containing M group capping agentis performed in the presence of an organic solvent, the method furthercomprising: conducting a solvent-exchange between the organic solventand an alternative carrier solvent.
 3. The method of claim 2 wherein theorganic solvent comprises one or more hydrocarbons.
 4. The method ofclaim 2 wherein the alternative carrier solvent comprises isododecane,2-butyloctanol, isohexadecane, C₁₂₋₁₅ alkyl benzoate, castor oil,hydrogenated palm oil, glycerin, isopropyl palmitate, cyclic siloxane,short-chain siloxane, or aliphatic hydrocarbon.
 5. The method of claim 1wherein the step of capping the bodied siloxane resin comprises heatingthe bodied siloxane resin and silicon-containing M group capping agentto a temperature ranging from 25 to 60° C.
 6. The method of claim 5wherein the step of heating the bodied siloxane resin and thesilicon-containing M group capping agent is conducted for a durationranging from 30 to 600 minutes.
 7. The method of claim 1 furthercomprising removing residual silicon-containing M group capping agentfrom the reaction vessel after the step of capping the bodied siloxaneresin.
 8. The method of claim 1 further comprising distilling residualsilicon-containing M group capping agent from the reaction vessel. 9.The method of claim 1 wherein the bodied siloxane resin capped with thesilicon-containing M group capping agent comprises the units:(R¹ ₃SiO_(1/2))_(a);(R² ₂SiO_(2/2))_(b);(R³SiO_(3/2))_(c);(SiO_(4/2))_(d), wherein: each R¹, R², and R³ is independently selectedfrom a substituted or unsubstituted carbon-containing group comprisingfrom 1 to 10 carbon atoms, an amino group, and a sulfido group, with theproviso that at least 0.40 mole of the R³ groups per mole of silicon inthe R³SiO_(3/2) units are propyl groups, and a+b+c+d=1.
 10. The methodof claim 9 wherein a ranges from 0.05 to 0.50, b ranges from 0 to 0.30,c is greater than 0, and d ranges from 0.05 to 0.60.
 11. The method ofclaim 1 wherein the bodied siloxane resin capped with thesilicon-containing M group capping agent has an initial molecular weight(M_(wi)) and an aged molecular weight (M_(wa)) after aging the bodiedsiloxane resin capped with the silicon-containing M group capping agentat 110° C. for 70 hours, wherein the M_(wa) increases 100% or less fromthe M_(wi).
 12. The method of claim 1 wherein said M_(wa) increases 50%or less from said M_(wi).
 13. The method of claim 1 wherein the bodiedsiloxane resin capped with the silicon-containing M group capping agentcontains less silanol groups than the bodied siloxane resin before beingcapped with the silicon-containing M group capping agent.
 14. The methodof claim 1 wherein the bodied siloxane resin capped with thesilicon-containing M group capping agent comprises from 0.02 to 0.20moles of silanol groups per mole of silicon.
 15. The method of claim 1wherein the bodied siloxane resin is selected from a group including:((CH₃)₃SiO_(1/2))_(a)(CH₃CH₂CH₂SiO_(3/2))_(c)(SiO_(4/2))_(d);((CH₃)₃SiO_(1/2))_(a)((CH₃)₂SiO_(2/2))_(b))(CH₃CH₂CH₂SiO_(3/2))_(c)(SiO_(4/2))_(d);((CH₃)₃SiO_(1/2))_(a)(CH₃)₂SiO_(2/2))_(b)((CH₃)(C₆H₅)SiO_(2/2))_(b′)(CH₃CH₂CH₂SiO_(3/2))_(c)(SiO_(4/2))_(d);((CH₃)₃SiO_(1/2))_(a)((CH₃)₂SiO_(2/2))_(b)(CH₃CH₂CH₂SiO_(3/2))_(c)(C₆H₅SiO_(3/2))_(c)(SiO_(4/2))_(d);((CH₃)₃SiO_(1/2))_(a)((CH₃)₂SiO_(2/2))_(b)((CH₃)(C₆H₅)SiO_(2/2))_(b′)(CH₃CH₂CH₂SiO_(3/2))_(c)(C₆H₅SiO_(3/2))_(c)(SiO_(4/2))_(d),and wherein a ranges from 0.05 to 0.5, the sum of b+b′ ranges from 0 to0.3, c ranges from 0.05 to 0.65, and d ranges from 0.05 to 0.6.
 16. Themethod of claim 1 wherein the silicon-containing M group capping agentis represented by the following general formula:

wherein: Z is Cl, an alkoxy group containing from 1 to 10 carbon atoms,or a hydrocarbyl group containing from 1 to 10 carbon atoms, each R⁴,R⁵, and R⁶ is independently hydrocarbyl groups containing from 1 to 10carbon atoms, X is O or NH, and y ranges from 0 to
 10. 17. The method ofclaim 1 wherein the silicon-containing M group capping agent comprisestrimethylchlorosilane, trimethylalkoxysilane, hexamethyldisiloxane, orhexamethyldisilazane.